"Yellow cake" is a uranium concentrate from ore-processing or leach-liquor processing plants. The processing plants use a variety of processes well known in the art to concentrate the uranium in the ore from conventional mining, or leach-liquor from uranium extraction in leaching processes into a more concentrated product suitable for ultimate purification.
The composition of crude plant yellow cake is dependent upon the type of process employed in concentrating the uranium from the uranium-containing ores. Most yellow cake currently produced in the United States contains mostly either ammonium diuranate or magnesium diuranate. Sodium diuranate is frequently the end-product of carbonate-leach processing plants.
Uranium concentrates (yellow cake) obtained in processing of leach fluids or ore contain usually about 70 to 85 weight percent uranium oxide calculated as U.sub.3 O.sub.8. The crude yellow cake must be further refined to produce materials actually useful in the energy and chemical industries.
The production of uranium metal and uranium compounds in a high state of purity is becoming increasingly important, particularly in view of the increased usages of nuclear energy to help alleviate the energy shortages being experienced in the more highly developed countries.
The refining of yellow cake generally has employed a dissolution step using nitric acid followed by a solvent extraction step using, for example, tributyl phosphate in hexane to extract uranium from the acidic aqueous phase. Recovery of the extracted uranium from the solvent phase is accomplished by stripping and precipitation.